Vitamin D3 alleviates the damage caused by high-fat and maintains lipid metabolism homeostasis in hepatopancreas by promoting fatty acid β-oxidation of Portunus trituberculatus

The purpose of present study was to evaluate the effects of vitamin D3 supplementation in high-fat diet on growth performance, calcium and phosphorus in tissue, immunity and lipid metabolism, and to explore whether adding vitamin D3 to high-fat diet can alleviate the adverse effects of high-fat diet on swimming crab (Portunus trituberculatus). The three experimental diets were normal fat diet (NFD, 9.35 % fat, 45.53 % protein), high fat diet (HFD, 14.69 % fat, 44.93 % protein) and high fat diet supplemented with 0.47 mg/kg VD3 (HFD+VD), respectively. A total of 108 healthy swimming crabs with an initial body weight of 9.42±0.13 g were selected for an 8-week feeding trial. The results showed that crabs fed with HFD+VD diet exhibited significantly higher percent weight gain (PWG), specific growth rate (SGR), feed efficiency (FE) and molting rate (MR) compared to those fed with HFD diet (P < 0.05). It was observed from hepatopancreas crude lipid content, TG content and hepatopancreas sections that HFD caused hepatopancreatic cell damage and abnormal lipid accumulation (P < 0.05), however, there were no significant differences in hepatopancreas crude fat content, TG content and hepatopancreas section observation between HFD+VD group and NFD group (P > 0.05). Crabs fed HFD diets with or without VD3 significantly down-regulated the expression of genes related to fatty acid transport, such as fabp9 and lpr1 in hepatopancreas (P < 0.05), moreover, the expression of genes related to fatty acid β-oxidation (cpt2 and acox1) were significantly up-regulated and genes related to lipid synthesis (fas and 6pgd) were significantly down-regulated in the hepatopancreas of the crabs fed with HFD+VD diet compared to those fed with HFD diet (P < 0.05). In conclusion, the results of present study indicated that a high-fat diet can cause deformation and rupture of hepatopancreas cells through abnormal lipid accumulation, thereby causing associated inflammation, leading to large calcium and phosphorus deposits in hemolymph and muscle, however, high fat diet supplemented with vitamin VD3 mainly enhanced the β-oxidation of fatty acids, inhibited lipid synthesis, alleviated abnormal lipid accumulation, and thus maintained the balance of lipid metabolism in hepatopancreas cells and promoted growth performance and feed utilization for swimming crab.